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	<div id="winchm_template_title">z (Execute While)</div>
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	<div id="winchm_template_content"><div id="mainSection"><p>The <b>z</b> command executes a command while a given condition is true.</p>
<p>User-Mode</p>
<pre class="syntax">Command <b>;</b> <b>z(</b> Expression <b>)</b> </pre>
<p>Kernel-Mode</p>
<pre class="syntax">Command <b>;</b> [Processor] <b>z(</b> Expression <b>)</b></pre>
<h2><a id="ddk_cmd_execute_while_dbg"></a><a id="DDK_CMD_EXECUTE_WHILE_DBG"></a>Parameters</h2>
<p></p>
<dl>
<dt><a id="_______Command______"></a><a id="_______command______"></a><a id="_______COMMAND______"></a>       <i>Command</i>      </dt>
<dd>
<p>Specifies the command to execute while the <i>Expression</i> condition evaluates to a nonzero value. This command is always executed at least once.</p>
</dd>
<dt><a id="_______Processor______"></a><a id="_______processor______"></a><a id="_______PROCESSOR______"></a>       <i>Processor</i>      </dt>
<dd>
<p>Specifies the processor that applies to the test. For more information about the syntax, see <a href="#Bookmark1931">Multiprocessor Syntax</a>. You can specify processors only in kernel mode.</p>
</dd>
<dt><a id="_______Expression______"></a><a id="_______expression______"></a><a id="_______EXPRESSION______"></a>       <i>Expression</i>      </dt>
<dd>
<p>Specifies the condition to test. If this condition evaluates to a nonzero value, the <i>Command</i> command is executed again and then <i>Expression</i> is tested again. For more information about the syntax, see <a href="#Bookmark1917">Numerical Expression Syntax</a>.</p>
</dd>
</dl>
<h3><a id="Environment"></a><a id="environment"></a><a id="ENVIRONMENT"></a>Environment</h3>
<table>
<tr>
<td>
<p><b>Modes</b></p>
</td>
<td>
<p>User mode, kernel mode</p>
</td>
</tr>
<tr>
<td>
<p><b>Targets</b></p>
</td>
<td>
<p>Live, crash dump</p>
</td>
</tr>
<tr>
<td>
<p><b>Platforms</b></p>
</td>
<td>
<p>All </p>
</td>
</tr>
</table>
<p> </p>
<h2>Remarks</h2>
<p>In many debugger commands, the semicolon is used to separate unrelated commands. However, in the <b>z</b> command, a semicolon separates the "z" from the <i>Command</i> parameter.</p>
<p>The <i>Command </i>command is always executed at least once, and then <i>Expression</i> is tested. If the condition is a nonzero value, the command is again executed, and then <i>Expression</i> is tested again. (This behavior is similar to a C-language <b>do - while</b> loop, not a simple <b>while</b> loop.)</p>
<p>If there are several semicolons to the left of the "z", all commands to the left of the "z" repeat as long as the <i>Expression</i> condition is true. Such commands can be any debugger commands that permit a terminal semicolon.</p>
<p>If you add another semicolon and additional commands after the <b>z</b> command, these additional commands are executed after the loop is complete. We do not typically recommend a line that begins with "z" because it generates uninteresting output forever unless the condition becomes false because of some other action. Note that you can nest <b>z</b> commands.</p>
<p>To break a loop that is continuing for too long, use <a href="#Bookmark2213"><b>CTRL+C</b></a> in CDB or KD, or use <a href="#Bookmark2915">Debug | Break</a> or CTRL+BREAK in WinDbg.</p>
<p>The following code example shows an unnecessarily complex way to zero the <b>eax</b> register.</p>
<pre class="syntax" xml:space="preserve"><code>0:000&gt; reax = eax - 1 ; z(eax)</code></pre>
<p>The following example increments the <b>eax</b> and <b>ebx</b> registers until one of them is at least 8 and then it increments the <b>ecx</b> register once.</p>
<pre class="syntax" xml:space="preserve"><code>0:000&gt; reax=eax+1; rebx=ebx+1; z((eax&lt;8)|(ebx&lt;8)); recx=ecx+1</code></pre>
<p>The following example uses C++ expression syntax and uses the pseudo-register <b>$t0</b> as a loop variable.</p>
<pre class="syntax" xml:space="preserve"><code>0:000&gt; .expr /s c++
Current expression evaluator: C++ - C++ source expressions

0:000&gt; db pindexcreate[@$t0].szKey; r$t0=@t0+1; z( @$t0 &lt; cIndexCreate )</code></pre>
<h2><a id="see_also"></a>See also</h2>
<dl>
<dt><a href="#Bookmark2003"><b>j (Execute If-Else)</b></a></dt></dl></div></div>	
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